1. Field of The Invention
The present invention relates generally to a yoke type reproducing magnetic head detecting signals to be recorded and stored in a magnetic recording medium.
2. Description of Related Art
In recent years, magnetic recording systems, such as hard disk drives, are rapidly miniaturized and densified, and expected to be further densified in future. In order to enhance the density in magnetic recording, it is required to narrow the recording track width to enhance the recording track density, and it is required to enhance the recording density in longitudinal directions of a recording track, i.e., the linear recording density,
However, in an inplane longitudinal recording system, there are problems in that, as the recording density increases, the demagnetizing field increases, the reproducing output decreases, and stable recording operations can not be carried out. As a system for eliminating these problems, the vertical recording system has been proposed. This vertical recording system is designed to carry out magnetization in directions perpendicular to the surface of a recording medium to carrying out recording. Even if the recording density is increased with respect to recording in longitudinal directions, the influence of the diamagnetic field is small and the lowering of the regenerative output is suppressed.
By the way, in either of the longitudinal recording or the vertical recording, an inductive head is conventionally used for reproducing medium signals. However, the AMR head which uses the anisotropic magnetoresistance effect and which has a high regenerative sensitivity is developed to be used as a shielded reproducing head so that a sufficient regenerative signal output can be obtained even if the recording track width becomes narrower and the magnitude of recorded magnetization decreases with the increase of density. In recent years, the spin-valve-type GMR head which utilizes the giant magnetoresistance effect (GMR) and which has a higher regenerative sensitivity is used, and the magnetic head is developed and studied for practical use.
In addition, in order to obtain a greater rate of change in resistance, it is proposed to use a magnetoresistance effect film (MR film) which is used in a system (vertical current applying (current perpendicular to plane) system) in which a sense current is caused to flow in a thickness direction (a direction perpendicular to the plane of the film), unlike the conventional system in which a sense current is caused to flow in a direction parallel to the principal plane of the film.
As a typical film which is used by causing a sense current to flow in thickness directions, there is a spin-tunneling type magnetoresistance effect (which will be also hereinafter referred to as TMR) film.
A conventional magnetic head using a vertical current applying MR film is disclosed in, e.g., Japanese Patent Laid-Open No. 11-316919. As shown in FIG. 21, in this conventional magnetic head, a vertical current applying MR film 75 comprises a free layer 71, an insulating layer 72, a pinned layer 73 and an antiferromagnetic film 74, and the contact area of an electrode 90 for supplying a sense current 78 to the vertical current applying MR film 75 is smaller than the film area of the vertical current applying MR film 75. Therefore, the magnetic field due to current, which is generated from the portion of the narrow electrode (pillar electrode) 90 joined to the vertical current applying MR film 75, influences the vertical current applying MR film 75. Furthermore, in FIG. 19, reference number 80 denotes an electrode film, reference number 82 denotes a magnetic domain, reference number 83 denotes an insulating film, reference number 85 denotes a through hole, reference number 92 denotes a top shielding film, and reference number 94 denotes a bottom shielding film.
In addition, an example of a vertical current applying MR film applied to a shielded magnetic head is disclosed in Japanese Patent Laid-Open No. 11-316919. Since a typical shielded head is used in a state that an MR film is exposed to a medium facing surface (which will be also hereinafter referred to as an ABS: Air Bearing Surface) to approach a recording medium, the shielded head can cause many magnetic fluxes to flow from the recording medium into the MR film, so that it has the merit of being capable of obtaining excellent regenerative sensitivity. On the other hand, the shielded head has the demerit of being easy to cause abrasion and deterioration of the MR film in the polishing of the ABS surface in the fabricating process, and the demerit of having the poor durability of the MR film while the medium is traveling.
Thus, magnetic heads having a high regenerative sensitivity have been developed. By using these magnetic heads, a recording signal begins to be able to be reproduced even if it has a very small recording bit size.
Since the scale down of the recording bit proceeds as the density is further enhanced in future, it is required to sensitively detect a small number of magnetic fluxes generated from a recording medium.
On the other hand, in order to enhance the linear recording density which is the density in longitudinal directions of a recording track, it is required to narrow the gap of a magnetic head. However, in the above described conventional magnetic heads using the magnetoresistance effect, a magnetoresistance effect element is put in a shield gap. Therefore, even in the case of the AMR head or the spin-valve GMR head, the thickness of the magnetoresistance effect element must be about 30 nm, and 70 nm between shields in view of insulation from the shields. For that reason, in the conventional type of magnetic heads, the thickness of the magnetoresistance effect element capable of narrowing the head gap is limited to about 70 nm. Therefore, there is a severe limit to the enhancement of the track recording density.
In addition, in magnetic recording systems such as hard disk drives, the flying height which is the distance between a magnetic head and a recording medium decreases with the enhancement of the recording density. The decrease of the flying height means that the probability of head's collision is increased by the slight protrusion of the recording medium. In fact, there is a problem in TA (Thermal Asperity) noise. Therefore, a yoke type head for drawing a magnetic flux into a magnetoresistance effect film via a yoke is preferably used so that the magnetoresistance effect film is not exposed directly to the medium facing surface. In the case of such a yoke type magnetic head, a structure that a magnetoresistance effect film is provided on a surface parallel to the medium facing surface is advantageous since the whole magnetoresistance effect film can be arranged in the vicinity of the medium. As such a structure, a horizontal yoke type magnetic head wherein a yoke and a magnetoresistance effect element are arranged in parallel to the plane of a substrate is proposed.
However, in the case of the horizontal yoke type magnetic head, it is required to increasingly decrease the size of the head with the enhancement of the recording density, and the magnetoresistance effect element must approach the medium facing surface. Although the photolithography technique progresses, an alignment precision of about tens nm is required to make a head having a sub-micron size. It is very difficult to prepare a head with such a precision.